Camshaft phasers for varying the timing of opening and closing of intake and exhaust valves in internal combustion engines are well known. Typically, the camshaft is driven by the crankshaft via a belt or similar. By arranging the belt around a part of the camshaft that can be rotationally adjusted (advanced or retarded) in relation to the camshaft the rotational phasing between the two shafts can be adjusted.
A common type of camshaft phaser is disclosed in e.g. US2007/0560539, DE102013212935, US2014/0150742 and WO2017/162233. This type is a so-called vane-type camshaft phaser generally comprising a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is supplied via an oil control valve to either the advance or retard chambers to change the angular position of the rotor relative to the stator, and consequently to change the angular position of the camshaft relative to the crankshaft.
As shown in e.g. DE102013212935 the oil control valve may form an elongated valve member arranged centrally inside the camshaft, where the valve member can be adjusted in a longitudinal direction of the camshaft so as to control the oil flow. The oil control valve member is controlled by means of an actuator arranged at the end part of the crankshaft, which actuator comprises a solenoid and a press pin adapted to press the valve member in an inwards direction. A spring arranged inside of the valve member is adapted to press the valve member in the opposite, outwards direction.
Some form of sealed cover is arranged around the oil control valve at the end part of the camshaft to prevent dirt etc. to enter the system and to avoid oil drainage/spillage but also to provide support for the actuator itself. Sealing is particularly important for avoiding exposing a dry belt that drives the camshaft to any oil.
Partly for the reason of reducing the risk of oil leakage, US2014/0366821 suggests the use of camshaft phasers actuated by an electric motor as an alternative to vane-type camshaft phasers. Long term experience of such devices appears, however, not yet to have been built up.
Conventional vane-type camshaft phasers with centrally mounted actuator have a disadvantage in some applications in that the actuator require a significant space at the end part of the camshaft, i.e. outside of the engine at the front thereof. This may be a problem, in particular for a passenger car having a transversely arranged engine where there is not much space at the front and end sides of the engine (which in such a case face towards the sides of the car).
In short there is thus a general need for improvements in the field of camshaft phaser arrangements.